1. Field of Invention
The present invention relates to a terminal structure of a connector including a female terminal having a tongue-piece-shaped spring contact disposed in a fitting portion thereof and a male terminal to be inserted into the fitting portion of the female terminal to contact with the spring contact.
2. Description of Related Art
Hitherto, when connecting together wire harnesses for a car, there is used a connector including a female terminal having a tongue-piece-shaped spring contact disposed in a fitting portion thereof and a male terminal having a male tab to be inserted into the fitting portion of the female terminal to contact with the spring contact; that is, by connecting together the male and female terminals, the wire harnesses can be electrically connected to each other.
For example, as shown in FIG. 9, in a fitting portion 1 of a female terminal 2 into which a male tab 3 of a male terminal 4 can be fitted, there are disposed a fixed contact 5, which can contact with one surface of the male tab 3, and a spring contact 6a, opposed to the fixed contact 5 with a given initial clearance. The male tab 3 is inserted between the two contacts 5, 6a and deforms the spring contact 6a elastically. While the spring contact 6a is elastically deformed in this manner, the male tab 3 contacts the two contacts 5, 6a to electrically connect a harness fixed to the female terminal 2 to a harness fixed to the male terminal 4.
In the above-mentioned structure, the initial clearance formed between the two contacts 5, 6a of the female terminal 2 is set at a value smaller by a given amount than the thickness of the male tab 3. Therefore, as the male tab 3 of the male terminal 4 is inserted into between the two contacts 5, 6a, the spring contact 6a is greatly deformed elastically to rapidly increase its contact reaction force. At the same time, as shown by a broken line in FIG. 7, just after the male tab 3 is inserted, the insertion force Fa of the male terminal 4 with respect to the female terminal 2 rises suddenly up to its peak value. Thereafter, the insertion force Fa decreases by a given amount, thereby bringing the two terminals 2, 4 into a connection-completed state.
Also, after the insertion of the male tab 3, as the insertion force Fa rises, the contact reaction force PLa of the spring contact 6a rises, as shown by another broken line in FIG. 7. Therefore, when the contact reaction force PLa of the spring contact 6a in the connection-completed state of the two terminals 2, 4 is set at a given value to thereby secure a contact pressure between the male tab 3 and spring contact 6a, the peak value of the insertion force Fa is inevitably caused to increase, which requires a large operation force when connecting together the two terminals 2, 4.
There has been a tendency, especially recently, that, as electronic equipment to be mounted in a car has been increasing in number, the number of terminals in connectors has been increasing. To cope with this trend, it is required that the arrangement pitch of the terminals is narrowed to thereby reduce the size of the connector, and that the insertion force per terminal is reduced to enhance the operation efficiency in connecting together the terminals. However, from the viewpoint of maintenance of the connection reliability of the connector, as described above, it is necessary that the contact reaction force of the spring contact is maintained at a given value. Therefore, it is difficult to further reduce the connecting operation force of the two terminals. This is a problem.
The present invention aims at eliminating the above-described problems. Accordingly, it is an object of the invention to provide a terminal structure of a connector which can reduce effectively the insertion force of a male tab with respect to the fitting portion of a female terminal without impairing the connection reliability of the connector.
According to a first aspect of the invention, there is provided a terminal structure of a connector including a female terminal, having a spring contact, e.g., a tongue-piece-shaped spring contact, in a fitting portion thereof, and a male terminal, having a male tab to be inserted into the fitting portion of the female terminal and contacted by the spring contact. When the male tab is fitted into the fitting portion of the female terminal, during the interval between a point of initial contact between the male tab and the spring contact and a point just before the insertion force of the male tab reaches its peak value, the contact angle xcex4L of the male tab with respect to the spring contact, and the friction coefficient xcexc between a surface of the male tab and a surface of the spring contact satisfy the following relational expression:
90xc2x0 greater than xcex4Lxe2x89xa790xc2x0xe2x88x92 tanxe2x88x921[(3xe2x88x925xcexc)/(5+3xcexc)].
According to the above structure, when the male tab is fitted into the fitting portion of the female terminal to connect together the male and female terminals, the contact reaction force of the spring contact can be set at a sufficiently high value, while preventing the insertion force of the male tab from suddenly increasing up to its peak value.
According to a second aspect of the invention, there is provided the terminal structure of the connector according to the first aspect of the invention, wherein during the interval between a point of initial contact between the male tab and the spring contact and a point just before the insertion force of the male tab reaches its peak value, the contact angle xcex4L of the male tab with respect to the spring contact, and the friction coefficient xcexc between the surface of the male tab and the surface of the spring contact satisfy the following relational expression:
90xc2x0 greater than xcex4Lxe2x89xa790xc2x0xe2x88x92 tanxe2x88x921[(1xe2x88x922xcexc)/(2+xcexc)].
According to the above structure, when the male tab is fitted into the fitting portion of the female terminal to connect the male and female terminals together, the peak value of the insertion force of the male tab can be reduced more effectively and also the contact reaction force of the spring contact can be set at a sufficiently high value.
According to a third aspect of the invention, there is provided the terminal structure of the connector according to the first aspect of the invention, wherein during the interval between a point of initial contact between the male tab and the spring contact and a point just before the insertion force of the male tab reaches its peak value, the contact angle xcex4L of the male tab with respect to the spring contact, and the friction coefficient xcexc between the surface of the male tab and the surface of the spring contact satisfy the following relational expression:
90xc2x0 greater than xcex4Lxe2x89xa753.74xc2x0xc3x97xcexc+59.537xc2x0.
According to this structure, when the friction coefficient between the surface of the male tab and the surface of the spring contact is in a range of from about 0.1 to about 0.4, the peak value of the insertion force, which is generated when the male tab is fitted into the fitting portion of the female terminal to connect the male and female terminals together, can be kept down to about 60% or less of the contact reaction force of the spring contact in the connection-completed state of the terminals.
According to a fourth aspect of the invention, there is provided the terminal structure of the connector according to the second aspect of the invention, wherein during the interval between a point of initial contact between the male tab and the spring contact and a point just before the insertion force of the male tab reaches its peak value, the contact angle xcex4L of the male tab with respect to the spring contact, and the friction coefficient xcexc between the surface of the male tab and the surface of the spring contact satisfy the following relational expression:
90xc2x0 greater than xcex4Lxe2x89xa753.74xc2x0xc3x97xcexc+63.936xc2x0.
According to the above structure, when the friction coefficient between the surface of the male tab and the surface of the spring contact is in a range of from about 0.1 to about 0.4, the peak value of the insertion force, which is generated when the male tab is fitted into the fitting portion of the female terminal to connect the male and female terminals together, can be kept down to about 50% or less of the contact reaction force of the spring contact in the connection-completed state of the terminals.
According to a fifth aspect of the invention, there is provided the terminal structure of the connector according to the first aspect of the invention, wherein during the interval between a point of initial contact between the male tab and the spring contact and a point just before the insertion force of the male tab reaches its peak value, the contact angle xcex4L of the male tab with respect to the spring contact is in a range of:
90xc2x0 greater than xcex4Lxe2x89xa767.5xc2x0.
According to this structure, when the friction coefficient between the surface of the male tab and the surface of the spring contact is about 0.15, the peak value of the insertion force, which is generated when the male tab is fitted into the fitting portion of the female terminal to connect together the male and female terminals, can be kept down to about 60% or less of the contact reaction force of the spring contact in the connection-completed state of the terminals.
According to a sixth aspect of the invention, there is provided the terminal structure of the connector according to the second aspect of the invention, wherein during the interval between a point of initial contact between the male tab and the spring contact and a point just before the insertion force of the male tab reaches its peak value, the contact angle xcex4L of the male tab with respect to the spring contact is in a range of:
90xc2x0 greater than xcex4Lxe2x89xa771.9xc2x0.
According to this structure, when the friction coefficient between the surface of the male tab and the surface of the spring contact is about 0.15, the peak value of the insertion force, which is generated when the male tab is fitted into the fitting portion of the female terminal to connect together the male and female terminals, can be kept down to about 50% or less of the contact reaction force of the spring contact in the connection-completed state of the terminals.
According to a seventh aspect of the invention, there is provided the terminal structure of the connector according to any one of the first to sixth aspects of the invention, wherein a forwardly-tapered inclined surface is formed at a leading end portion of the male tab. When the male tab is fitted into the fitting portion of the female terminal, a base end portion of the inclined surface contacts the spring contact.
According to the above structure, when the male tab is fitted into the fitting portion of the female terminal, the base end portion of the inclined surface contacts the spring contact. Therefore, the contact angle of the male tab is not decided in accordance with the inclination angle of the inclined surface. The contact angle xcex4L of the male tab with respect to the spring contact of the female terminal can be set at a proper value, regardless of the inclination angle of the inclined surface.
These and other objects, advantages and salient features are described in or are apparent from the following detailed description of exemplary embodiments.